Siren Song
by Nev827
Summary: When Castle and Beckett go undercover in a nightclub, Castle as himself and Beckett as a singer, something unexpected happens that changes their relationship forever. Disclaimer: The song in this story was written by Paul McCartney, not me
1. Chapter 1

Siren Song

World-famous playboy murder mystery novelist Richard Castle entered the night club Anthemusa dressed in one of his best suits, but with his tie loosened and his top shirt button undone. The idea behind his look was to make others think he was stopping in for some drinks after a long evening of public appearances. Hopefully, the attractive celebutantes that frequented the club would notice, allowing him to work his magic while NYPD Detective Kevin Ryan, undercover as an assistant manager, and his partner Detective Javier Esposito, also undercover but as a bartender, would scope out the crowd for the club's owner. Detective Kate Beckett, the beautiful, tough, and intelligent woman whom Castle had been shadowing for the previous three years and who served as his inspiration for his wildly successful Nikki Heat series of novels, would also be undercover, but Castle didn't know in what capacity. He secretly hoped it wasn't as a waitress.

Two weeks prior, "Beckett and the boys," as they had come to be known around the NYPD's 12th precinct, had begun working a series of murders of young women in an upscale part of the city. As their investigation progressed, they came to suspect that the night club's owner was behind the murders. It seemed he was using the club as a recruiting ground for girls he could force into a prostitution ring. And anyone who decided they wanted out of their so-called "waitressing gig" ended up dead.

The catch was that the club's owner was rich, handsome, and cocky, so they all agreed that he wasn't likely to go quietly, nor was he likely to make it easy for them to collar him. But arrogance was arrogance, so they figured the lord wouldn't be able to resist presiding over his manor – especially if he got wind of the fact that a celebrity of Castle's stature might drop in. So Castle leaked it to a few gossip magazine reporters he knew that he'd come by tonight after a public appearance. Sure enough, when Castle arrived in his limousine (an idea suggested by the detectives' boss Captain Roy Montgomery to heighten the effect and impact of his arrival) the paparazzi were stationed outside and the bar was crowded with young, attractive, star-struck coeds in low cut tops with Sharpies at the ready in case New York's Ninth Most Eligible Bachelor was feeling up to some chest-signing.

Castle worked his way towards the bar, pausing frequently to shake hands with a prominent personage he knew or, more frequently, to sign a boob that was thrust into his face. Once he reached the bar, he ordered a martini from Esposito, making sure not to blow the detective's cover. He spotted Ryan in the crowd as well, conferring with the club's general manager, who was in on the sting and wanted nothing more than to put an end to the owner's nefarious reign. Thank goodness someone still had a sense of civic duty.

Things were going just as planned and right about the time Castle wondered when Beckett would show up, the general manager appeared on a stage located directly opposite from the bar where Castle was holding court. He held a microphone and introduced the night's entertainment – a fresh new talent just into town who he fantastically characterized as a direct descendant of the infamous Greek Sirens – Lily. A smattering of applause broke out and a piano struck up a slow, sultry melody. Here we go, Castle thought: another pop-tart wannabe who doesn't even have a quarter of the talent that even the best backup singer in Nashville has. He turned to take another swig from his drink, then almost dropped his glass when he caught a glimpse in the corner of his eye of the woman introduced as Lily. It was Beckett.

She was wearing the red Jimmy Choo heels and matching strapless, and rather short, red dress that she always wore in one of Castle's fantasies where the two of them flirt incessantly over a game of pool. She took the microphone and adjusted its stand with the same amount of confidence with which she had so many times entered one of the interrogation rooms at the precinct to question a perp.

"Now that is entertainment," Castle quipped to Esposito the bartender, just as a bar patron might casually observe to any bartender. Esposito gave Castle a nod.

"I saw her rehearse earlier," the detective said, keeping in character. "Man, what a babe."

Castle momentarily wanted to shoot Esposito a shocked look and smack him across the face, but he remembered that such behavior would blow the act. He composed himself internally and did his best to cover up his brief surprise as the detective continued.

"It would not surprise me in the least if she really was a Siren's descendant." With that, he hurried off to help another customer, while Beckett began her performance. Castle recognized the song as The Way It Should Be, originally performed by Paul McCartney and featured in the recent film The Lake House.

"_I'm very sure this never happened to me before…"_ Beckett began singing. Her voice was velvety smooth and sultry as sultry could be. Castle had no idea Beckett was such a talented singer. He knew she had had some dance training from the one time they had danced while also undercover at a charity gala not long after Castle began shadowing her. She had followed his movements that night almost as if she could read his mind. He hoped that she couldn't do so right now.

Her singing was getting to him in a way he hadn't expected. Yet another layer of that Beckett onion she teased him about has been revealed, he thought. She owned the stage as she sang, scanning the audience and carefully gauging their reactions to her rendition, so she could adjust her performance and give them what they wanted. Her obvious confidence in her ability to entertain astounded Castle. She worked the microphone and used her voice as Leonardo used a brush to paint the _Mona Lisa_ or Michelangelo used a hammer and chisel to sculpt _The Pieta_.

For her part, Beckett felt something completely foreign coming over her. It had nothing to do with the fact that she hadn't sung in front a crowd in many years. It was the fact that this man, whose books she had read, whose fan site she had trolled, and for whose autograph she had once stood in line for hours to get, was more than likely watching her. She worked the crowd, scanning for the owner or anything unusual, making eye contact with those who seemed to be particularly enjoying her singing, then moving on to others. She closed her eyes, used her hands to accentuate the song, and moved slowly to the music while holding the mike stand like a seasoned singer.

" …_I met you and now I'm sure _

_This never happened before. _

_Now I see _

_This is the way it's supposed to be. _

_I met you and now I see this is the way it should be._

_This is the way it should be for lovers_

_They shouldn't go it alone._

_It's not so good when you're on your own…"_

She finished the first verse and spied Castle in the crowd. He was watching more intently than she had expected. From his position across the room, she could feel his eyes boring into her soul, not undressing her like she had felt so many times before, but simply taking everything about her in while tuning everything else out. She decided to have a little fun with him and looked deep into his eyes. Two can play at this game, she thought, remembering how easy a mark he was. I'll lead him to water, only to snatch the cup from his thirsty lips at the last second. So she gave her singing a more seductive, pleading dimension with the second verse.

"…_So come to me..."_

Their eyes locked.

"…_Now we can be what we wanna be._

_I love you…"_

Castle's heart was racing now, not in lust like it had so many other times in the past, but in wonder. This woman who was still an enigma in so many ways, but had proven herself his equal in intelligence, wit, sauciness, heart, and passion had blown him away.

Beckett's heart was racing too. When she sang the line "I love you," a tingling, energizing feeling she hadn't expected, nor ever felt this strongly before flowed through her veins. Being a passionate, attractive woman she had naturally felt those tingles and flutters before, but typically they had come and gone like a windstorm. This feeling qualified as a major hurricane that in her heart of hearts she knew was not going to just blow over when the case was closed and she went home. She was now a total slave to the music. Her rational side had gone into hibernation and she sang and moved without inhibition, without regard to anything else in the world. All that existed was her, the intelligent, fun, charming, and handsome Richard Castle and the music.

"…_And now I see_

_This is the way it should be._

_This is the way it should be…"_

There was no denying it now, Castle thought. She wasn't just performing for the crowd now, she was singing to him. She was finally putting into words what both of them had been feeling from the beginning of their partnership: that something about this was right, that their paths had intersected for a reason. Fate had brought them together and was now telling them as they stood with eyes transfixed on each other, that this is what they were each meant for. They were meant to be together. As the song said "this is the way it should be."

Beckett knew there were only a few lines in the song left. She knew she had to make the most them. I've gone this far, she figured, why not go all the way with it. Hold nothing back. I can never find the words to tell him how much I respect him, how he's brought me out of such a dark place and shown me so much light, how thankful I am for our partnership, and how much I've grown to care for him, and now, love him. Her rational side made a comeback and tried to stop her, but she quickly buried those thoughts and continued.

"…_This is the way it should be for lovers…"_

She sang with conviction, putting as much meaning into every syllable as she could muster.

"…_They shouldn't go it alone._

_It's not so good when you're on your own…"_

Castle saw her swallow hard after singing these lines. He suddenly wanted to bolt towards the stage to and look deeper into her eyes, in hopes that his being closer to her would bring her some comfort and reassurance that he'd always be around. For her part, Beckett was now struggling to hold it together. The thought that those last two lines brought to her mind were unbearable. If Castle left, he would take with him a chunk of her being, as well as her heart.

"…_I'm very sure_

_This never happened to me before._

_I met you and now I'm sure_

_This never happened before…"_

Beckett closed her eyes.

"…_This never happened before._

_This never happened before…"_

She held the last note until after the music had stopped and slowly opened her eyes, looking upon Castle meaningfully. Even though he was across the club, Castle could see tears had welled in her eyes. She recovered long enough to smile and take a small bow as applause rang throughout the bar then hurried nervously off the stage. Oh no, Castle thought. She's come to her senses. It's all over that fast. He suddenly remembered the martini he was holding and turned his back to the stage. As he stared into the bottom of his glass while swirling the drink, he felt Esposito the Fake Bartender approach him.

"Some song, huh, Mr. Castle?" he asked casually, but with a knowing look on his face. Detective Ryan also sent him a meaningful smile from his assigned perch overlooking the crowd.

"Yeah," Castle answered. "Some song."


	2. Chapter 2

The club owner never showed that night. The case would go on. As Castle sat in a taxicab on his way home, he couldn't get Beckett's performance out of his head. Is it possible she loved him? Is it possible he loved her back? Yes, he answered himself, and he felt a wave of relief and energy wash over him in the cab's backseat. He loved her. He'd always loved her, since they met. Who was he kidding denying it? Despite this realization, Beckett's seeming refusal to admit to her feelings ate at him. She had spent the entire time as the team reviewed the evening's events back at the precinct avoiding him. Could he have simply been taken in completely by a masterful performance given by a woman he admired and was attracted to? No, this was more. His feelings ran deeper. He knew it in every nerve in his body. And every fiber of his being told him that her feelings ran deeper too. Nevertheless, his mind would not be at rest on the issue. He told the cab driver to take him to Beckett's apartment building instead of his own. He would find out.

He stood in front her door and thought for a second. There's still time to change your mind. You can just let it be and let things go on as before. No, things couldn't possibly go on as they did before. Things were different now. He took a breath and knocked. No answer. He knocked one more time before she finally opened the door, wearing pajamas and rubbing sleep out of her eyes.

"Castle, it's late. What on earth are you doing here?" she asked.

"I'm sorry, but I can't sleep. Can I come in?"

"What? Do you need me to tuck you in or something?" she joked. When his face didn't return her humor, she quickly wiped the smile off her face and invited him in. She could tell that whatever was bothering him was a serious matter.

"Well?" she asked.

"I enjoyed your performance tonight," he began tentatively.

Her expression changed quickly from questioning to as serious as his. She looked down at the floor for a moment and swallowed hard before speaking.

"About that, um, it's just that it'd been a while since I sang in front of an audience and it felt good. Really good … to be on stage and in front of a crowd … singing," she explained nervously, her eyes darting all over her apartment.

"I'll bet it felt good. It looked like it felt good," Castle replied and took a step towards her.

"Castle…"

"Beckett … Kate… just hear me out," he interrupted. "I may be a sucker for an attractive woman and I may not be the best at keeping my feelings to myself…"

Beckett grinned slightly and nodded, but Castle persisted.

"But I'm not an idiot. I know you weren't just singing tonight."

"What do you mean?" she asked, her eyes intensely searching his and waiting for the answer she desperately wanted to hear.

"You know what I mean." He took a couple more steps closer to her. "You were singing to me. Telling me something. Something you've obviously been feeling for a long time. Something that I've been feeling for a long time too. And it wasn't until tonight, when I heard you sing that beautiful song to me, that I figured out what it is."

Beckett's heart was pounding just as it was when his eyes met hers at the club. He knows, she thought. What am I going to do? We're partners. She had made up her mind a long time ago that dating someone you work with was never a good idea. But was it really, she wondered? Did she really believe that or was that just one of the defense mechanisms she always put up to save herself from getting hurt. She didn't want to, but she continued searching his eyes for an answer to her own question. How she wanted to lose herself in his embrace, to be closer to him, touch him, feel him, experience everything about him. Then she remembered his reputation. Could she trust him? If they were going into a run-down warehouse to apprehend a suspect, yes, but when faced with a beautiful, intelligent woman without any emotional hang-ups? She didn't know. How could she admit her feelings if she couldn't trust him in that way? She made up her mind about what to do.

"Castle, I don't know what you think you saw or experienced tonight, but you're mistaken," Beckett bluffed, trying as hard as she could to hide the difficulty she had in speaking. "I wasn't singing to you. I was playing a part. Performing. Like I do every day in the interrogation room at the precinct."

"Then why did your eyes well up when you finished? Why did you hurry off stage and why did you avoid me for the rest of the night?" Castle challenged.

"I was embarrassed because I just got caught up in things. I saw you looking at me and I was reluctant to tell you the truth. I thought you'd be hurt when I told you that it wasn't real," she finished, hoping beyond hope that she wouldn't have to put up with the charade much longer.

Castle did nothing but look her deeply in the eyes. He wasn't entirely positive, because he knew she had an excellent poker face, but he thought she was bluffing. "Your eyes tell me that it was and still is very real." Castle pushed.

Beckett could barely hold it together now. Castle had not only struck a nerve, but had seen right through her again. That was one thing that she both loved and hated about him – she couldn't hide when he was around. They hadn't worked together that long and yet he already knew her too well.

"Castle…"

"Call me Rick."

"No I won't call you Castle … er … Rick, or … dammit the point is I just can't," she finally choked out.

"So I'm right. You do feel something," he answered excitedly.

"No! I just … even if I did have feelings for you, we work together. The last thing I want to deal with and to have everyone else deal with while we try to solve cases together is a soap opera. Trust me when I say that it isn't happening now and it's not ever going to happen in the future." Her bottom lip quivered momentarily as she finished, but she again recovered quickly and steadied herself, signaling that she wasn't about to change her mind.

Castle still refused to believe that she was being honest with him, but he also knew the look on her face. He had seen it the first time he had offered to help her solve her mother's murder. The discussion was over. The issue was closed. He would leave it alone from now on, only because he loved her so much.

"Fine," he said, hurt and angry. Then a thought hit him. There might be one more way to crack the Beckett nut. "Then there's just one thing left to do."

"What's that?" she asked somewhat impatiently.

He stepped forward, took hold of her upper arms and pulled her into a long, passionate kiss. Just as she had put all her unspoken words and feelings towards him into her song earlier tonight, he tried to do the same with his lips and his hands and his entire body. He felt her tense up initially and feared that his plan would backfire by causing her to run from him. But he didn't care. He, too, had come far and saw no reason to turn back.

He broke away, looked her in the eye one more time, then turned to leave for the night. As he did, he felt her grab his wrist to stop him.

"Wait Rick," she said, the toughness and stubbornness in her voice now gone. Just as he had thought, the kiss had broken the dam behind which she kept her strongest feelings of love. Having thought she had succeeded in convincing him that he was wrong, the last thing Beckett was expecting in that moment was for him to kiss her. And what a kiss that was. She found herself defenseless as soon as his lips met hers. Just as she did earlier, she allowed herself to be swept away by the outgoing tide of his passion. Then he broke away and started to leave. And without a thought in her head, other than a feeling of how empty she would feel if she wasn't honest with him right then, she reached out for his hand to stop him. It was the furthest she had ever put herself out there for any man, and for the first time in her life, she wasn't scared, but blissfully happy.

"What?" he asked.

"You're right," she said breathlessly, her eyes swimming with emotion. "Initially I was just singing. Actually, I was just teasing you, but then I saw you and looked into your eyes … and all of sudden nothing mattered, but you and me and … the fact that I love you."

Castle didn't say anything immediately, just stood still smirking. "Can you do me a favor?" he finally asked.

"What's that?" Beckett queried as every pressure point in her body tingled with anticipation.

"Remember this date every time you tell me that I don't know what I'm talking about or that I'm being crazy or that you can't stand working with me," he answered grinning widely.

"From now on this will be remembered as the anniversary of the date when I succeeded in getting you to admit that I was right," he mocked subtly.

She couldn't help but laugh as she fell into his arms. They kissed again, but more even more passionately than before because each knew the other's feelings were true. This time Beckett returned Castle's kiss, matching his passion and running her hands over his back while he stroked her hair. They surrendered to each other and to their own long suppressed desires. There was nothing else in the world that mattered to them except being in the moment. With their arms entwined around the other's body and mouths locked together, they were no longer Castle & Beckett, but one unit of kindred souls united after a long, lonely search for the missing half that would make them whole. After a few minutes, they broke apart, but kept their arms around each other.

"I love you Kate," Castle said sincerely. "I don't think I've ever loved anyone as much as I love you right now."

"Rick, I love you too. More than I ever thought I could love anyone, especially after Mom died," Beckett replied, her voice trembling slightly at the thought of her mother's death. "And I don't want to hide it anymore."

"Well, I don't know that we'll be able to after that performance, which by the way was H-O-T, hot."

Beckett blushed at his compliment.

"Besides, I'm pretty sure Esposito figured it out," Castle continued. "He did, after all, call you a babe."

Beckett raised her eyebrows in questioning disbelief. When Castle nodded back at her, she shook her head slowly. He'll pay for that one, she thought.

"And if he knows, then Ryan knows," Castle finished. "And if they both know, then…"

"Lanie knows," Beckett interrupted him. "I already called her and told her what happened. You know, because I'm a woman and that's just what we do," she finished matter-of-factly.

"Ah," Castle said and a smile crept across his face. "I guess I'll have to behave myself from now on when we go to the morgue."

"Not necessarily," Beckett said seductively and she leaned in towards him until her mouth was inches from his. "You see, I love you even more when you're naughty."

"Do you now?" Castle asked playfully and touched his forehead to hers. "Well then, shall I show you just how naughty I can get?" he said, eyes wide as a child's on his or her birthday and his voice matching her seductive tone.

"Bring it on." Beckett teased and Castle laughed and lifted her off the ground into a warm hug.


End file.
